Statistical characteristics of atmospheric phase fluctuations observed by a VLBI system using a beacon wave from a geostationary satellite

This paper reports the statistical characteristics of phase fluctuations obtained by a very long baseline interferometry, which received beacon waves from a geostationary satellite. Observations were made in different weather conditions by the 6-m Kagoshima and the 10-m Mizusawa radio telescopes, which were 1284 km apart from one another. Atmospheric phase fluctuations ranging from 0.2 to about 1000s were detected. To study a variety of statistical characteristics of these phase fluctuations, the Allan standard deviation, sigma(y)(T), the temporal structure function, D,5(7), and the square root of power spectrum, G(phi)(f), were calculated from the observation results. These qualities were found to depend on the time interval T or the frequency f (f = 1/2T) as follows: sigma(y)(T) proportional to T-0.6, T-0.3, D-phi(T) proportional to T-0.9, T-1.3 for 0.2 s < 7 < 1.5 s and 1.5 s < T < 400 s. G(phi)(f) proportional to f(-0.8) for 2.5 Hz > f > 0.33 Hz and G(phi)(f) proportional to f(-1.3) for 0.33 Hz > f > 0.00125 Hz. The curves of sigma(y)(T) and D-phi(T) exhibited shifts whose magnitudes followed the weather order clear, cloudy, and rainy. For T > 1.5 s (or f < 0.33 Hz), the experimental results were consistent with the theoretical values predicted by Kolmogorov's turbulence theory and a frozen-screen model, but for T < 1.5 s (or f > 0.33 Hz), the model has to be modified to explain the experimental results.